title: Microenvironmental studies of pre-B and B cell development in human and mouse fetuses.
abstract: Immunofluorescence techniques were used to trace the development of cells expressing mu heavy chains in humans and mice. IgM B cells were distinguished from pre-B cells by their additional expression of kappa or lambda light chains. Generation of pre-B and progeny B cells was evident in hemopoietic fetal liver and bone marrow, but not in thymus, heart, lung, spleen, kidney, and placental tissues. Pre-B and B cells, in a ratio of 2 to 1, were abundant in sections of hemopoietic liver and in bone marrow from 12- to 15-wk-old human fetuses, whereas these cells were rare in nonhemopoietic liver samples obtained beyond the 34th week. In mouse fetal liver mu+ cells appeared first around the 12th day of gestation and increased in frequency throughout the third trimester. On day 17 of gestation, kappa light chain expression by 1% of mu+ cells was noted, and the percentage of kappa+/mu+ cells increased progressively to more than 80% by 5 days after birth. Pre-B and B cells were interspersed among myeloid and more abundant erythropoietic cellular elements in the extrasinusoidal areas adjacent to hepatic cords. A loose clustering or "starburst" distribution pattern of pre-B cells became evident around day 17. These observations suggest a model for in situ generation of pre-B and progeny B cells in the hemopoietic fetal liver. In the midst of more numerous erythropoietic elements, immunoglobulin-negative precursors divide to generate a loose colony of mu+ pre-B cells that divide again before giving rise to a wave of IgM B cells.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology; D002454:Cell Differentiation; D004912:Erythrocytes / Q000166:cytology / Q000276:immunology; D005260:Female; D005333:Fetus / Q000166:cytology* / Q000276:immunology; D005455:Fluorescent Antibody Technique; D005865:Gestational Age; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000276:immunology; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics / Q000276:immunology; D007148:Immunoglobulin mu-Chains / Q000235:genetics / Q000276:immunology; D008099:Liver / Q000166:cytology / Q000276:immunology; D008168:Lung / Q000166:cytology / Q000276:immunology; D051379:Mice; D010641:Phenotype; D010920:Placenta / Q000166:cytology / Q000276:immunology; D011247:Pregnancy; D013154:Spleen / Q000166:cytology / Q000276:immunology
chemical_list: D007143:Immunoglobulin Heavy Chains; D007148:Immunoglobulin mu-Chains